This is an application to purchase a modern, analytical electron microscope and accessory X-ray spectrometer for use by researchers in the Cell and Virus Building at Roswell Park Memorial Institute. There are presently three 18-year-old research quality transmission electron microscopes (TEMs) in the Cell and Virus Building plus an inexpensive low power electron microscope. There is no analytical microscope anywhere in the Buffalo area. We would like to purchase a new Hitachi H-600-2 microscope to replace one of the old TEMs. The new microscope offers numerous advantages not provided by the older instruments. Foremost among these is electron beam scanning capability which allows the microscope to operate as a scanning electron microscope (SEM) or scanning transmission electron microscope (STEM) as well as in the conventional transmission mode (TEM). Spectral analysis of the x-rays generated when the scanning beam strikes the specimen (also called energy dispersive X-ray spectroscopy or EDX) allows identification and quantitation of all the higher mass atoms of which the specimen is composed. This application contains specific proposals for use of the new capabilities of the proposed microscope by each of the 13 researchers who will be using the new instrument extensively.